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Stock-based Compensation - Classification of Stock-based Compensation (Detail) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended
Apr. 30, 2015
Apr. 30, 2014
Stock-based compensation:    
Total stock-based compensation $ 5,482us-gaap_AllocatedShareBasedCompensationExpense $ 2,874us-gaap_AllocatedShareBasedCompensationExpense
Cost of revenue [Member]    
Stock-based compensation:    
Total stock-based compensation 124us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_CostOfSalesMember		 59us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_CostOfSalesMember
Research and development [Member]    
Stock-based compensation:    
Total stock-based compensation 3,094us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_ResearchAndDevelopmentExpenseMember		 1,590us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_ResearchAndDevelopmentExpenseMember
Selling, general and administrative [Member]    
Stock-based compensation:    
Total stock-based compensation $ 2,264us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_SellingGeneralAndAdministrativeExpensesMember		 $ 1,225us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_SellingGeneralAndAdministrativeExpensesMember